A contract is valid as to form if made in conformity with: (1) the law of the state of making; (2) the law of the state of performance to the extent that performance is to be rendered in that state; (3) the law of the state of common domicile or place of business of the parties; or (4) the law governing the substance of the contract under Articles 3537 or 3540.
Nevertheless, when for reasons of public policy the law governing the substance of the contract under Article 3537 requires a certain form, there must be compliance with that form.